1. Field of the Invention
The present invention relates to the purification/treatment of impure liquid media by adsorbing objectionable contaminants therein onto an activated charcoal; such active charcoal is introduced into such media in the form of a unit dosage purifying amount thereof sealedly packaged within a film of a water dispersible/soluble polymer, notably polyvinyl alcohol.
2. Description of the Prior Art
It is known to this art that active charcoals are materials produced by carbonization of various carbonaceous substrates, e.g., wood, coal or polymers, and which have been subjected to an activation treatment which confers upon such substrates a high porosity and a high adsorbing power or capacity. Such properties have long been exploited for the separation or purification of gases and for the decoloration, purification or deodorization of liquids.
Industrial applications; of active charcoals for the treatment of liquids are very numerous and also well known to this art, both in the food sector (refining of sugarbeet sugar or cane sugar, production of glucose or lactose, treatment of white wines, ciders or fruit juices, production of glutamic acid or of pectin, and the like), and in the chemical sector (production of tartaric acid, glycerol, and the like) or in various industrial treatments (recovery of solvents, spent plating baths, degassing of drilling muds, and the like).
For all of the above applications, a problem is presented regarding the handling and use of such charcoals. When the treatment can be carried out by percolation, charcoals are used that have been obtained directly in the form of rods or granules obtained from powder. But it is the powder, because it permits intimate contact between the charcoal and the liquid to be purified, which constitutes both the simplest and the most efficient form thereof.
The amounts of charcoal employed, on the order of one kilogram per cubic meter, do not substantially alter the rheology of the liquids treated, the contact time can be as prolonged as desired, and the separation of the charcoal from the purified liquid is easily carried out by settling or by filtration. All of the sequences where the charcoal is introduced wet, or dispersed in the liquid, are conducted with the greatest of ease; on the other hand, the preliminary operations suffer from the difficulties inherent in the handling of any dry powder, in particular those which relate to the low apparent density of the uncompacted charcoal, and also to a certain heterogeneity when wetted. These disadvantages have been partially remedied by using charcoals packaged in the form of fragmentable granules which disintegrate when immersed in a liquid. This, however, is but a partially satisfactory solution in the sense that a perfectly fragmentable granule is an impossible compromise between a rapid spontaneous dispersion of the charcoal in the liquid and the absence of dusting on storing and handling.